A group of lawmakers led by Sen. Elizabeth Warren, D-Mass., and Rep. Jared Polis, D-Colo., sent a letter to President Trump on Wednesday urging him to restore Obama-era guidelines that allowed states to determine their own marijuana laws.

Earlier this month, Attorney General Jeff Sessions rescinded the Cole Memorandum, a 2013 directive from the Obama administration that directed U.S. attorneys to place a “low priority” on enforcing federal marijuana laws in states that have legalized pot. To date, nine states (Alaska, California, Colorado, Maine, Massachusetts, Nevada, Oregon, Vermont and Washington) and the District of Columbia have passed laws allowing the recreational use of marijuana. Dozens more have passed laws legalizing it for medicinal use.

Sessions’ decision to rescind the guidelines, the lawmakers said, “will have a chilling effect” in those states.

“This action by the Department of Justice has the potential to unravel efforts to build sensible drug policies that encourage economic development as we finally move away from antiquated practices that have hurt disadvantaged communities,” reads the two-page letter, which was signed by 54 members of Congress, 51 of them Democrats. Three Republicans — Alaska Rep. Don Young, California Rep. Dana Rohrabacher and Florida Rep. Matt Gaetz — signed it, too.

The lawmakers pointed out that as a candidate Trump signaled that he would leave marijuana laws “up to the states.”

When @realdonaldtrump ran for president he said marijuana policies should be left up to states. He should stick to his word and let states implement their own regulations – upending them only creates confusion, and puts our public health & safety at risk. https://t.co/pFNvbWzdr2

The letter urged Trump to follow the “will of the voters” and allow states to “provide common sense, responsible regulations for marijuana that balance public health and public safety needs with limited criminal justice resources.”

Polis and Sen. Cory Gardner, R-Colo., who threatened to block all nominees to Justice Department posts in response to Sessions’ decision, sent a similar letter to Trump on Jan. 4, the day Sessions rescinded the Cole memo.

“I’m prepared to hold every Justice Department nominee until Jeff Sessions lives up to what he told me, lives up to his commitment,” Gardner tweeted the same day.

I am prepared to take all steps necessary, including holding DOJ nominees, until the Attorney General lives up to the commitment he made to me prior to his confirmation.

In an interview with Yahoo News, the Colorado Republican said that, prior to confirmation as attorney general, Sessions had assured him that the Trump administration would not be harsh on the state-driven push toward legalization.

“Jeff Sessions told me this wouldn’t be a priority. Jeff Sessions told me the policy would not be reversed, and today Jeff Sessions went back on his word,” Gardner said. “He said, ‘This is just not something that President Trump is focused on.’ And apparently, it’s not just a focus, it’s a primary initiative of the new year.”

A subsequent meeting with Sessions did nothing to assuage Gardner’s concerns.

“The meeting went as I expected it,” Gardner told NBC’s Chuck Todd shortly after his sit-down with Sessions. “He’s going to hold his position for now; I’m going to hold my position.”

“I’m somebody that didn’t support the legalization of marijuana in Colorado,” Gardner said. “But I also think it’s necessary to protect that state decision.”

Last March, a bipartisan group of senators, including Warren and Lisa Murkowski, R-Alaska, asked the Justice Department to uphold the Obama-era policy allowing individual states to determine their own pot laws after then-White House press secretary Sean Spicer suggested that the Trump administration might press for “greater enforcement” of federal pot laws.

“We respectfully request that you uphold DOJ’s existing policy regarding states that have implemented strong and effective regulations for recreational marijuana use,” the senators wrote in a letter to Sessions. “It is critical that states continue to implement these laws.”

“When @realDonaldTrump ran for president he said marijuana policies should be left up to states,” Warren tweeted on Thursday. “He should stick to his word and let states implement their own regulations – upending them only creates confusion, and puts our public health & safety at risk.”